(NNC)Ru(II) Complex Catalyzed Selective Functionalization of Ketones with Methanol: Understanding the Role of Ancillary Ligands

Abstract

Employing a single catalyst and substrate, the selective synthesis of all probable products upon varying the reaction conditions is uniquely challenging and exciting to explore. Utilizing methanol, cyclometalated (NNC)Ru(II) complex catalyzed selective transformation of a wide variety of ketones to the corresponding alcohols, β-methylated alcohols, and α-methylated ketones is disclosed. Notably, by changing the reaction parameters, the selective synthesis of all the probable products for the reactions of ketones with methanol was achieved. For these transformations, the role of different ancillary ligands (DMSO, CH3CN and PPh3) coordinated to the Ru(II) center was investigated. This protocol was successfully applied for the functionalization of a few pharmaceutically important molecules and to sterically hindered α, α′-disubstituted and α, α′, α′′-trisubstituted ketones. Several control experiments, kinetic studies, Hammett studies, and DFT calculations were carried out to understand this catalytic process.